As display devices have become larger and thinner in recent years, plasma display panel (hereinafter referred to as PDP) devices, for example, have been under development, and at the same time there has been growing need for this devices to be recycled.
As shown in FIG. 8, a PDP is generally configured such that a front substrate 81 and a rear substrate 82, both made of glass, are sealed together with a sealing material (not shown), and a discharge gas is charged in between the sealed front substrate 81 and rear substrate 82 to form a discharge space. Display electrodes 83, but electrodes 84, a dielectric layer 85, and a protective layer 86 are formed in that order on the front substrate 81. Address electrodes 87 are formed on the rear substrate 82, and these are each coated with a red, green, or blue phosphor 89 via a dielectric layer 88. As shown in the drawing, the red, green, and blue phosphors 89 on the address electrodes 87 are separated from each other by barriers 90 (see, for example, Patent Documents, 1, 2, and 3).
In the past, rejects from manufacturing processes, and electrical products that have been used as products have generally been disposed of by being buried and so forth. In the case of the above-mentioned PDPs, because they contain hazardous substances such as lead in the sealing material or the various layers formed on the front substrate 81 and rear substrate 82, they have to be buried after the hazardous substances have first undergone a solidification treatment. Also, large glass substrates have been used for the front substrate 81 and the rear substrate 82 in order to provide a larger screen. Consequently, the substrates account for greater volume and weight in a product, and recycling is therefore also desirable from the standpoints of cost and the environment. A method for recycling as an industrial material a glass substrate used for the front or rear substrate of a PDP, which has become a reject in the course of manufacture, has been disclosed in the past (see, for example, Patent Document 4).
FIG. 9 shows the conventional procedure in which a recycling procedure S11 is incorporated into a PDP production procedure S10. The details of S10 are not given here, but upon completion of an aging step S95, reject identification is performed in a glass inspection step S96. Any PDP determined here to be defective is sent to S11. S11 comprises mainly a step S98 of separating the front and rear substrates incorporated into a recovered PDP, a step S99 of peeling the layers (surface layers) formed on the separated front and rear substrates, and steps S100 and S101 of separating and recovering the peeled components of the surface layers of the front and rear substrates. Here, in S100, the front and rear substrates are finely crushed into glass cullet (hereinafter referred to as cullet) in order to recycle as glass raw materials the front and rear substrates whose surface layers have been removed.
Patent Document 1: Japanese patent publication No. 2,503,072
Patent Document 2: Japanese published unexamined patent Application No. H4-366526
Patent Document 3: Japanese published unexamined patent Application No. S55-70873
Patent Document 4: Japanese published unexamined patent Application No. 2002-50294